The present invention relates generally to gas turbines and, more particularly, to a gas turbine and method of reducing a bucket tip shroud creep rate by selectively removing cutter teeth on a seal rail of a bucket tip shroud.
In certain turbine designs, the bucket tip shrouds, constructed of a nickel-base superalloy, are prone to creep damage that may eventually lead to creep rupture and material loss. Creep rates in a gas turbine component are determined by the environmental conditions in which the component is placed. Tip shroud material loss can result in partial shroud-to-shroud contact with adjacent buckets. Such an occurrence may result in a forced outage, which obviously is disruptive and time-consuming to correct any damage.
Previous designs for bucket tip shrouds have included a scalloped configuration, which configuration helps to reduce the shroud lifting due to creep, but still fails to prevent creep damage at the high stress and high temperature fillet area. Redesigned buckets intending to solve the creep problems include features such as restacked airfoil, added cooling holes, different fillet sizes, more scalloped shrouds, etc.